$source="D:\SVN\Privat\Codeplex\SP2010ListManager\trunk\AppUI\Images\"
$dest=$source+"Org\"
$gnu="GNU.png"
Get-ChildItem -Path $source -Filter "*.png" | 
    where {$_.Length -ne 2646} | 
    foreach-object -process{ 
        if(-not (Test-Path $dest$_)) 
            {
                echo $a$_; 
                Move-Item $_.FullName -Destination $dest$_;
                Copy-Item $source$gnu $_
            }
        }
